In the design of weighing systems for use in combination with packaging machines wherein a predetermined quantity of materials are weighed and then generally transported by gravity to the packaging machine for filling in a bag, the problem of controlling the flow of materials from the weighing station to the packaging machine is a critical one in order to try to have a smooth flow of materials so that dust problems are minimized.
Historically, the weighing scale manufacturer generally fulfilled his obligation when the desired net weight of the product was secured in the weighing container at which point the bottom of the container would be opened up and the product would be permitted to drop or rapidly flow to the bag in the bag packaging portion of the system passing through a void and having no restraint on the product or control of the product. From this it can be seen that many problems would be encountered especially in the control of the flow of the materials in the weighing hopper especially from the standpoint of generation of dust and removal of dust from the hopper transition chute.
It can be understood that an extreme dusty atmosphere can occur in the transition chute of a packaging system where the product drops anywhere from 5 to 10 feet from the bottom of the weighing scale to the bottom of the bag. The problem can be amplified when the product being packaged is, for example, manganese sulfate which is extremely fine and flows in the transition chute much like water flows in a pipe. Other types of materials which were troublesome from the standpoint of material flow and dust control were granular carbon and also granular celulose acetate.